This application relates to a method for controlling an engine to allow a driver to obtain a working range of the engine in excess of a base working range thereof. In another aspect, the application relates to a system for controlling an engine to allow a driver to obtain a working range of the engine in excess of a base working range thereof. The engine is preferably an engine for a heavy vehicle, such as a lorry or truck.
Fuel economy is an increasingly important subject to the world's fleets of heavy vehicles, motivated both by economy and by environmental concerns. In order to delimit the fuel consumption during transports with heavy vehicles, it has been suggested to control the driving patterns of the drivers of the vehicles.
For example, it is common practice to set a maximum road speed limit (RSL) for a fleet of vehicles, which maximum road speed limit cannot be exceeded by the driver of the vehicle. Generally, only the manager of the vehicle fleet or the owner of a single vehicle may access the control so as to set said road speed limit.
However, in certain driving situations, it may be a disadvantage to be limited to the maximum road speed limit, such as during an overtaking or passing of another vehicle.
In US 2001 0044690, a system and method for controlling an engine in a vehicle is proposed, which allows the vehicle operator to manually request a vehicle speed in excess of the established vehicle speed limit. This method includes setting a normal vehicle speed limit, setting a passing duration period, setting a passing override reset interval, and controlling the engine in response to operator input to provide a greater vehicle speed for a cumulative period not greater than the passing duration period at any time during the passing override reset interval.
It is desirable to find an alternative solution for controlling the driving patterns of the vehicle so as to, at least to some extent, meet the requirements of fuel economy and of vehicle versatility when driving.
According to an aspect of the present invention, a method is provided for controlling an engine to allow a driver to obtain a working range of the engine in excess a base working range thereof, the method comprising                establishing a base working range, which limits are defined by a base torque versus engine speed curve,        establishing an excess working range, which limits are defined between said base torque versus engine speed curve and an excess torque versus engine speed curve, the excess torque versus engine speed curve displaying a higher maximum torque level and/or a higher end engine speed as compared to the base torque versus engine speed curve,        establishing an excess availability limit, defining the maximum duration or maximum distance of access to the excess working range per unit time or unit distance,        calculating a cumulative consumed excess value per unit time or unit distance by summating any time periods or distances during which the excess working range is accessed within the unit time or unit distance; and        controlling the engine in response to driver input to allow access to the excess working range only when the cumulative consumed excess value is less than the excess availability limit.        
In accordance with the invention, the engine control method with the purpose to improve and reduce fuel consumption is not based only on controlling the vehicle speed. Instead, the torque versus engine speed curve of the engine of the vehicle is considered.
In an engine, the available torque is defined by a torque versus engine speed curve (See FIG. 1).
In FIG. 1, an example of a torque versus engine speed curve is depicted, which displays an approximately constant maximum torque over a relatively wide range of engine speeds. Thereafter, the torque curve slopes downwards towards higher engine speeds, indicating a lower available maximum torque at higher engine speeds. Finally, the torque declines to zero torque, where the engine speed corresponding to zero torque corresponds to the end engine speed.
It shall be understood that many different variants of torque versus engine speed curves are possible, the shapes varying for different engines. The example curves of the figures are hence to be seen as non-limiting examples only.
The term “end engine speed” as used herein is sometimes referred to with the term “end governed engine speed”, and is defined as the engine speed corresponding to zero torque.
In accordance with the invention, there is established a base torque versus engine speed curve. The area below the base torque versus engine speed curve illustrates the base working range within which the engine is intended to work, and may be set by logics in the engine control system to a level dimensioned to improve fuel consumption while still enabling the engine function to perform adequately considering the loads involved.
In addition to the base torque versus engine speed curve, an excess torque versus engine speed curve is defined. This curve will have a higher maximum torque and/or a higher end engine speed than the base curve (See FIG. 2). An excess working range of the engine is defined between the excess torque versus engine speed curve and the base torque versus engine speed curve. Accordingly, each engine speed value in the excess working range corresponds to the same or a higher torque value than on the base torque versus engine speed curve.
Again, various shapes of the base torque versus engine speed curve as well as the excess torque versus engine speed curve are possible, giving rise to different areas forming the excess working range. The invention is not restricted to the shapes of the examples in FIGS. 1 and 2.
In accordance with the invention, torque and engine speed are controlled rather than the speed of the vehicle hosting the engine, which vehicle speed is controlled in many prior art methods. Controlling torque and sometimes allowing excess torque has the advantage that the torque may not only be used to obtain a higher vehicle speed (even if this is of course possible). Instead, the excess torque could be used for example to enable the driver to maintain vehicle speed when driving uphill.
When the excess torque versus engine speed curve displays a higher end engine speed, this means that it is possible to maintain torque at a higher engine speed as compared to the base torque versus engine speed. This is sometimes referred to as having a “longer” engine, with which it possible to stay more often with a lower gear, which also may increase the comfort for the driver when driving.
Also, the control of the torque versus engine speed curve may be combined with controlling power, e.g. to allow excess power during similar circumstances as those explained below. This enables access to excess performance level (torque and power) of the engine.
In accordance with the invention, access to the excess working range of the engine is restricted. The basic idea is that the excess working range should only be available a fraction of the time used for driving, or expressed differently, a fraction of the distance travelled when driving. Time and distance are both suitable parameters for controlling the availability of the excess working range.
Hence, it is suggested to establish an excess availability limit, which may be seen as a buffer including a certain amount of access to the excess working range per unit time or distance.
Moreover, it is suggested to regularly or continuously calculate a cumulative consumed excess value per unit time or distance. The cumulative consumed excess value will indicate the amount of access to the excess working range which has already been used within the unit time or distance.’
Access to the excess working range will be allowed only when the cumulative consumed excess value is less than the excess availability limit, in other words when the used amount of access to the excess working range is less than the buffer amount—the excess availability limit.
When time is used as a parameter, the excess availability limit will be the maximum duration of access to the excess working range per unit time. For example, the excess availability limit could be 5 minutes per hour (5 min/60 min).
During, driving, it in this case is suggested to calculate a cumulative consumed excess value per unit time by summating any time periods during which the excess working range is accessed within the unit time. For example, if the driver accesses the excess working range for 1 minute, then for 2.5 min, and then for 0.5 min within an hour, the cumulative consumed excess value at the end of that hour would be 1+2.5+0.5=4 min.
The engine is to be controlled in response to driver input to allow access to the excess working range only when the cumulative consumed excess value is less than the excess availability limit. Accordingly, in the example above, the cumulative consumed excess value of 4 min is less than the excess availability limit of 5 min, meaning that new access to the excess working range should be allowed for another 1 min during this static time limitation of 1 hour.
Alternatively, the excess availability limit may be defined using distance, as the maximum distance of access to the excess working range per unit time. For example, the excess availability limit could be 8 km/100 km.
In this case, the cumulative consumed excess value may be calculated per unit distance by summating any distances during which the excess working range is accessed within the unit distance. For example, if the driver accesses the excess working range for 2 km, then for 3 km, and then for 1 min within a drive of 100 km, the cumulative consumed excess value at the end of those 100 km would be 2+3+1=6 km.
The engine is to be controlled in response to driver input to allow access to the excess working range only when the cumulative consumed excess value is less than the excess availability limit. Accordingly, in the example above, the cumulative consumed excess value of 6 km is less than the excess availability limit of 8 km, meaning that new access to the excess working range should be allowed.
Moreover, the availability of the excess working range could be controlled using both time and distance as parameters. For example, limits could be set for both time and distance, whereafter a minimum choice calculation of the two could be used to control availability.
In one embodiment of the invention, the excess availability limit is a constant, preset maximum excess availability limit. For example, the excess availability limit may be 5 minutes or 8 km, the value being constant while driving.
In another embodiment however, the excess availability limit may be a dynamic value, meaning that the value may alter e.g. during a drive. One preferred example of a method using a dynamic excess availability limit is a method using a leaky bucket” counter to calculate the excess availability limit. In this case, e.g. any time period of driving without using the excess working range adds time to the excess availability limit (fills the bucket), but only to a preset, maximum excess availability limit. Any time period of driving while using the excess working range will not add time to the excess availability limit.
Alternatively, the bucket may be filled (time may be added to the excess availability limit) also during time where the excess working range is used. The periods of use of the excess working range are generally very short in relation to the periods without the excess working range, meaning that their contribution to the excess availability limit is not crucial for the final excess availability limit.
For example, it could be determined that for every 10 minutes of driving without using the excess working range, the excess availability limit is added to with one minute. After 50 minutes of driving without using the excess working range, the excess availability limit is up to 5 minutes, being the maximum excess availability limit. Continued driving without using the excess working range will not increase the excess availability limit.
At this point, the driver may use all of the 5 minutes, that is the driver could access the excess working range for a full 5 minutes, if desired. If so, the excess availability limits drops to 0, and the driver must driver for 50 minutes without using the excess range in order to refill the excess availability limit completely. If instead only 1 minute of driving in the excess working range is perfumed, the excess availability limit drops to 4 minutes, and the driver must drive another 10 min without the excess range, in order to obtain the maximum excess availability limit.
A dynamic excess availability limit, of the type exemplified above or of another design, could be advantageous since it may be used to encourage the driver to “save” excess working range.
Generally, the “filling” of the bucket should take place relatively slowly, i.e. the fill time is a fraction of the actual driving time during which the bucket is filled.
The above applies mutatis mutandis when the excess availability limit is expressed as maximum distance of access per unit distance instead of in maximum duration per unit time.
When a drive is finalized, the excess availability limit at the end of the drive may be stored. The excess availability limit may be stored in a memory in the vehicle control system, so as to be available when the same vehicle is used again. Alternatively, the excess availability limit may be saved as personalized information, e.g. on a Driver Card, belonging to the driver, and hence he accessible to the driver at his/her next drive, also if another vehicle is used.
In an embodiment of the invention a method is proposed wherein, for each unit time or unit distance, the cumulative consumed excess value is set to zero at the start of the unit time or unit distance, and the cumulative consumed excess value per unit time or unit distance is calculated at any time or distance by summating the time periods or distances during which the excess working range is accessed during the unit time or distance.
For example, if a driver accesses the excess range for 1 minute, then for 2.5 min, and then for 0.5 min within an hour, the cumulative consumed excess value at the end of that hour would be 1+2.5+0.5=4 min. However, as the first hour expires, the cumulative consumed excess value is reset to zero, and the calculation restarts for the second hour of driving. (The case will be similar if distance is used instead of time.)
Alternatively, a method is proposed wherein the cumulative consumed excess value per unit time or unit distance is calculated at any time or distance by summating the time periods or distances during which the excess working range is accessed within the most recent unit tune or unit distance.
For example, if a driver starts driving at 00.00, and then accesses the excess range for 1 minute finishing at 00.10, then for 2.5 minutes finishing at 00.30, and finally for 0.5 minutes finishing at 00.50, the cumulative consumed excess value at 00.50 hours will be 1+2.5+0.5=4 min. However, if the driver continues to drive until 01.20 without using the excess range, the new cumulative excess value at 01.20 will only regard the passed time period from 00.20. Accordingly, the cumulative excess value at 01.20 will only be 2.5+0.5=3 min. (The case will be similar if distance is used instead of time.)
Accordingly, only the most recent unit time or unit distance is considered. This option might again be advantageous as it will encourage the driver to save access time to the excess working range.
Preferably, the method could include that, during time periods or distances when access to the excess working range is allowed, exceeding a preset road speed limit is also allowed. In this case, the control using the torque versus engine speed curve is combined with a control of road speed limit as known in the prior art.
Advantageously, the method could include that, during time periods or distances when access to the excess working range is allowed, exceeding a preset acceleration limit is also allowed.
In one alternative, the base torque versus engine speed curve and/or excess torque versus engine speed curve are static. The curves being static mean that they are constant when driving.
In another alternative, the base torque versus engine speed curve and/or excess torque versus engine speed curve are dynamic. The curves being dynamic mean that the may alter or vary throughout the drive.
Preferably, at least one of the base and the excess torque versus engine speed curve is dynamic so as to be determined using the vehicle gross weight as input. In this case, the curve or curves may be adapted to the weight of the vehicle so that a sufficient engine is allowed with consideration to the load.
Preferably, at least one of the base and the excess torque versus engine speed curve is dynamic so as to be determined using the present road profile as input. In this case, the curve or curves may alter when driving so as to meet the demands on the engine caused by the environment, e.g. whether the vehicle is travelling, in a flat or in a hilly landscape. Advantageously, the driver input for requesting access to the excess working range is performed via a dedicated throttle function, preferably of “kick-down” type. This is advantageous since, although the function is convenient as being easy to reach and to control, a “kick-down” function is perceived as somewhat demanding to the driver, so that there is an experience of having to “work” for the excess working range. This contributes to the overall perception that use of the excess working range should be a rare occurrence.
Alternatively, the driver input for requesting access to the excess working range may be performed via a control panel, preferably a button on a control panel.
When using a button, e.g. a push button, this control could be used to give access to the excess working range for a limited time period/distance. This limited time could preferably be set by a timer. Alternatively, access could be allowed for the time during which the driver has an excessive demand, which is indicated by him/her giving full throttle.
Moreover, the two alternatives above may be combined.
Advantageously, the excess availability limit could be temporarily increased following a time period or distance during which a preferred driving pattern was used. Such a driving pattern could be defined as desired, promoting e.g. eco-driving (fuel saving), safe driving etc. Driving patterns could be monitored using numerous in-vehicle systems such as data from the engine and from other systems, from GPS systems etc.
Preferably, such a preferred driving pattern may be defined as driving in a predefined reward area of the base torque versus engine speed curve. For example, the reward area may comprise a combination of high torque with low engine speed, which corresponds to top gear lagging down when driving. Since driving in this area is particularly economic when it comes to fuel consumption, time or distance of driving in this manner could be rewarded by extra excess availability limit, and/or a reduction of the cumulated consumed excess value (used time or distance in excess working range).
Advantageously, an available excess value may be calculated by subtracting the cumulative consumed excess value from the excess availability limit, said available excess value being available to the driver. Accordingly, the driver may be aware of how much time or distance in the excess working range is allowable at each time or distance.
Advantageously, data regarding the time periods or distances during which the excess working range is used may be stored in a memory for use in driving statistics.
In another aspect, in accordance with the invention there is provided an engine control system for controlling an engine to allow a driver to obtain a working range of the engine in excess of a base working range thereof, the system comprising a memory for storing                the base working range, which limits are defined by a base torque versus engine speed curve,        the excess working range, which limits are defined between said base torque versus engine speed curve and an excess torque versus engine speed curve, the excess torque versus engine speed curve displaying a higher maximum torque level and/or a higher end engine speed as compared to the base static torque versus engine speed curve,        an excess availability limit, defining the maximum duration of access to the excess working range per unit time or unit distance; and        
a processor unit for                calculating a cumulative consumed excess value per unit time or unit distance by summating any time periods or distances during which the excess working range is accessed within the unit time or unit distance; and        controlling the engine in response to driver input to allow access to the excess working range only when the cumulative consumed excess value is less than the excess availability limit.        
In yet another aspect, there is provided a computer program comprising program code means for performing all the steps of any one methods as described above when said program is run on a computer.
In yet another aspect, there is provided a computer program product comprising program code means stored on a computer readable medium for performing all steps of anyone of the method as described above when said program product is run on a computer.
In yet another aspect there is provided, a vehicle comprising an engine control system which enables control of the engine in accordance with the method as described above.
Similar reference numbers indicates similar features in the drawings.